Re: dgraph, tlist, tcon: MSVC error due to array of flexible structs

--===============1298710873665286055==
Content-Type: multipart/signed; micalg=pgp-sha256;
	protocol="application/pgp-signature"; boundary="qYrsQHciA3Wqs7Iv"
Content-Disposition: inline


--qYrsQHciA3Wqs7Iv
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Sep 22, 2016 at 10:31:16PM -0600, Kevin Locke wrote:
1;4803;0c> Hi all,
>=20
> Building dgraph using Microsoft Visual C++ produces the following
> error:
>=20
> dgraph.h(25): error C2233: 'edge': arrays of objects containing
> zero-size arrays are illegal
>=20
> The issue is that MSVC supports flexible array members, but does not
> support arrays of structs with flexible array members.  My
> understanding is that such support is not required by C99 or C11, but
> I don't know whether such support is common beyond Clang/GCC.
>=20
> Is there any interest in supporting such compilers?  If so, I can see
> a few potential fixes:
>=20
> 1. Change TCON to use flexible array members only when the compiler
> supports arrays of structs with flexible array members.  This is an
> easy fix, but wastes space for every TCON/TLIST usage on such
> compilers.
>=20
> 2. Have TCON (and TLIST) provide an alternative macro which uses
> flexible array members only when supported in arrays, and use that in
> dgraph.  It would increase the API and duplicate a bit of code, but
> would only waste space when TCON/TLIST are placed in arrays.
>=20
> 2. Replace the 2-element edge array in struct dgraph_node with
> separate fields edge_from and edge_to.  This complicates the logic a
> bit, since it is no longer symmetric with dgraph_edge.  It would also
> be an incompatible API change.
>=20
> 3. Change TLIST to use TCON_WRAP?  I don't understand TLIST/TCON well
> enough to know if this is really an option.  Hopefully an expert can
> weigh in here.

I've now done this for tlist and several other modules, we should have
a much better chance of compiling on windows.

--=20
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

--qYrsQHciA3Wqs7Iv
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=J7ha
-----END PGP SIGNATURE-----

--qYrsQHciA3Wqs7Iv--

--===============1298710873665286055==
Content-Type: text/plain; charset="utf-8"
MIME-Version: 1.0
Content-Transfer-Encoding: base64
Content-Disposition: inline

X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KY2NhbiBtYWls
aW5nIGxpc3QKY2NhbkBsaXN0cy5vemxhYnMub3JnCmh0dHBzOi8vbGlzdHMub3psYWJzLm9yZy9s
aXN0aW5mby9jY2FuCg==

--===============1298710873665286055==--